Photovoltaic tiles, roofing system, and method of constructing roof

ABSTRACT

There are provided photovoltaic tiles (each containing at least one photovoltaic cell) which can be readily integrated into a roof structure constructed of standard roofing materials. The photovoltaic tiles have frames which hold photovoltaic elements, the frames having end portions which are engageable with opposite end portions of similarly-shaped photovoltaic tiles and/or with end portions of standard roofing tiles, and/or which are shaped similar to shapes of end portions of standard roofing tiles. There are also provided roofing systems including standard roofing tiles and such photovoltaic tiles. There are also provided methods of constructing a roof using such a roofing system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a CONTINUATION APPLICATION of U.S. application Ser.No. 10/608,201, filed Jun. 27, 2003, and claims the benefit of U.S.Provisional Patent Application No. 60/392,341, filed Jun. 27, 2002, theentirety of which is incorporated herein by reference,

FIELD OF THE INVENTION

The present invention is directed to photovoltaic tiles in which eachphotovoltaic tile contains one or more photovoltaic cells, and which canbe integrated into a roof structure constructed of standard roofingmaterials. The present invention is further directed to a roofing systemincluding standard roofing tiles and one or more photovoltaic tiles ofthe present invention. The present invention is also directed to amethod of constructing a roof using a roofing system according to thepresent invention.

BACKGROUND OF THE INVENTION

Solar energy collection is of great importance and is of ever-increasingimportance, particularly in light of limitations and environmentalconcerns associated with other sources of energy, and the resultingever-increasing demand for “alternative” energy (i.e., non-fossil fuelenergy).

Photovoltaic modules have been deployed in a wide variety of ways,including deployment on the roofs of buildings, including private homes.However, such panels have not been capable of being readily integratedinto roof structures constructed of standard roofing materials, placinga limitation on the usage of photovoltaic modules in a variety oflocations where solar energy could otherwise be collected. For example,many communities prohibit the mounting of conventional photovoltaicmodules on the front roofs of homes because the conventionalphotovoltaic modules cannot be effectively integrated into roofstructures constructed of standard roofing materials.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, there are providedphotovoltaic tiles (each containing at least one photovoltaic cell)which can be readily integrated into a roof structure constructed ofstandard roofing materials. The present invention is further directed toa roofing system including standard roofing tiles and one or morephotovoltaic tiles of the present invention. The present invention isalso directed to a method of constructing a roof using a roofing systemaccording to the present invention. The present invention provides roofsin which photovoltaic tiles are securely fastened to the roof, in whichthe photovoltaic tiles lay close to the roof surface, and/or in whichthe photovoltaic tiles provide a high degree of uniformity andsimilarity in dimension to the roofing tiles. These structural featuresmake it possible to integrate the photovoltaic tiles of the presentinvention with standard roofing tiles to provide an integrated structurewhich is aesthetically improved compared to conventional photovoltaicoptions.

According to the present invention, there is provided a photovoltaictile which has at least one end portion which is engageable with an endportion of another similarly-shaped photovoltaic tile and/or an endportion of a standard roofing tile.

In one aspect of the present invention, there is provided a photovoltaictile which has first and second end portions which have respectiveshapes which are substantially identical to the shapes of first andsecond side portions of a standard roofing tile, such first and secondside portions being shaped such that a first side portion of one of suchstandard roofing tiles is engageable with a second side portion of asecond such standard roofing tile.

The present invention is directed to a photovoltaic tile, comprising atleast one photovoltaic element having at least one photovoltaiccollection surface; and a frame extending around an edge of thephotovoltaic element, the frame holding the photovoltaic element inplace relative to the frame.

In one aspect of the present invention, the frame comprises a first endportion having a shape which is engageable with a shape of the secondend portion, such that a pair of photovoltaic elements can be engagedwith each other by engaging the first end portion of one with the secondend portion of the other.

In another aspect of the present invention, the frame comprises a firstend portion having a shape which is engageable with at least a firstside portion of a standard roofing tile. Preferably, the frame furthercomprises a second end portion having a shape which is engageable with asecond side portion of the standard roofing tile.

In a further aspect of the present invention, the frame comprises afirst end portion having a shape which is similar to at least a firstside portion of a standard roofing tile.

In addition, the present invention is directed to a roofing systemcomprising a plurality of roofing tiles and at least one photovoltaictile as described above. The present invention is further directed to aroofing system which further comprises a roof deck on which the roofingtiles and the at least one photovoltaic tile are mounted, and preferablyalso a support structure on which the roof deck is supported.

The photovoltaic elements described above preferably each comprise atleast one photovoltaic cell mounted in a casing. Preferably, thephotovoltaic elements each have a dead space in order to provide anoverlap, e.g., an area where a portion of a tile in a row (course) oftiles mounted lower on a roof is overlapped by portions of tiles in acourse mounted farther up the roof.

In a preferred aspect of the present invention, the width of the frame(i.e., the dimension in the direction in which the tiles in a course arearranged) is a multiple of the width of the roofing tile, so that eachphotovoltaic element can be mounted so as to occupy an area where one ormore roofing tiles would fit, thereby providing the ability to providecontinuity in an overall pattern of a roof structure which includesroofing tiles and photovoltaic tiles.

The present invention is further directed to a method of constructing aroof, comprising positioning on a roof surface at least one roofing tilehaving a first side portion and a second side portion and at least onephotovoltaic tile, such that a first end portion of the frame of thephotovoltaic tile is engaged with a first side portion of the roofingtile.

The present invention is further directed to a method of constructing aroof, comprising positioning on a roof surface at least a firstphotovoltaic tile and a second photovoltaic tile, such that a second endportion of the frame of the second photovoltaic tile is engaged with afirst end portion of the frame of the first photovoltaic tile.

In addition, the present invention is directed to a method ofconstructing a roof, comprising positioning on a roof surface aplurality of roofing tiles and a plurality of photovoltaic tiles, eachof the roofing tiles having a first side portion and a second sideportion, each of the photovoltaic tiles comprising a frame having afirst end portion and a second end portion, such that each first endportion is engaged with a second end portion of another frame or with asecond side portion of one of the roofing tiles, and such that eachsecond end portion is engaged with a first end portion of another frameor a first side portion of one of the roofing tiles.

The invention may be more fully understood with reference to theaccompanying drawings and the following description of the embodimentsshown in those drawings. The invention is not limited to the exemplaryembodiments and should be recognized as contemplating all modificationswithin the skill of an ordinary artisan.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a schematic view of a preferred embodiment of the top of aphotovoltaic element which is suitable for use according to the presentinvention.

FIG. 2 is a perspective view of an example of a standard roofing tile.

FIG. 3 is a perspective view of a front end of a first embodiment of aframe according to the present invention.

FIG. 4 is a perspective view of the back side of the front frame memberof FIG. 3.

FIG. 5 is a cross-sectional view of a left end portion of a firstphotovoltaic tile, a roofing tile engaged with the first photovoltaictile, and a right end portion of a second roofing tile engaged with theroofing tile, according to a second embodiment of a frame according tothe present invention.

FIG. 6 is a cross-sectional view of a front portion of a frame of aphotovoltaic tile according to the second embodiment.

FIG. 7 is a cross-sectional view of a rear portion of a frame of aphotovoltaic tile according to the second embodiment.

FIG. 8 is a cross-sectional view of a left end portion of a firstphotovoltaic tile, a roofing tile engaged with the first photovoltaictile, and a right end portion of a second roofing tile engaged with theroofing tile, according to a third embodiment of a frame according tothe present invention.

FIG. 9 is a cross-sectional view showing a roofing tile applied to aroof in one course, a photovoltaic tile applied to the roof in a nextcourse, and a second photovoltaic tile applied to the roof in a furthercourse.

FIG. 10 is a perspective view depicting photovoltaic tiles engaged withother photovoltaic tiles, photovoltaic tiles engaged with roofing tiles,and a roofing tile engaged with another roofing tile.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned above, the present invention provides photovoltaic tiles(each containing at least one photovoltaic cell) which can be readilyintegrated into a roof structure constructed of standard roofingmaterials.

The photovoltaic tiles according to the present invention each includeat least one photovoltaic element and a frame which holds thephotovoltaic element in place relative to the frame.

FIG. 1 depicts a preferred embodiment of a photovoltaic element 10 whichis suitable for use according to the present invention. In thephotovoltaic element 10 shown in FIG. 1, eighteen photovoltaic cells 11are encapsulated in a transparent casing 12, preferably made of glass.The photovoltaic element 10 shown in FIG. 1 includes a dead space 13,where no photovoltaic cells or portions of photovoltaic cells arepresent.

A variety of photovoltaic cells are known in the art, e.g., structureswhich can separate charges, such as p-i-n devices, photo-electrochemicaldevices (e.g., Graätzel Cells, such as those disclosed in U.S. Pat. Nos.4,927,721 and 5,084,365, the entireties of which are hereby incorporatedby reference) and p/n junction devices, as well as quantum dot deviceswhich separate charges due to differences in recombination rates betweenelectrons and holes. The invention is applicable to these and any otherphotovoltaic cells.

In the case of p/n junction devices, as is well known, a photovoltaiccell comprises at least one diode comprising at least one n-type regionand at least one p-type region. The n-type region and the p-type regionare in contact with each other, so as to form a p-n junction. In orderto maximize the surface area of solar collection, photovoltaic cellstypically have a substantially flat surface which faces the source oflight (e.g., the sun).

Typically, such photovoltaic elements further include n-type region andp-type region contact layers, an antireflective, substantiallytransparent coating over the n-region contact layer, a transparent coverglass over the antireflective coating, a junction box, and electricallead lines (often referred to as “pigtails”), all of which are wellknown in the art. The electrical lead lines of a number of photovoltaicelements can be connected (e.g., using “quick connectors”) in series tocombine the power produced by such photovoltaic elements.

The photovoltaic element 10 depicted in FIG. 1 has a frame which has afront edge 14, a left edge 15, a right edge 16 (opposite the left edge15), a back edge 17 (opposite the front edge 14), a photovoltaiccollection surface (on the top, facing out of the page) and a bottomsurface (opposite the photovoltaic collection surface). A junction boxcan be positioned at any suitable location as is well known in the art,e.g., on the bottom of the photovoltaic element.

The frame preferably extends around an edge of the at least onephotovoltaic element, and holds the at least one photovoltaic element inplace relative to the frame. In one aspect of the present invention, theframe comprises a first end portion and a second end portion, the firstend portion having a shape which is engageable with a shape of thesecond end portion, such that a pair of such photovoltaic elements canbe engaged with each other by engaging the first end portion of one withthe second end portion of the other.

In another aspect of the present invention, the frame comprises a firstend portion having a shape which is engageable with at least a firstside portion of a standard roofing tile. Preferably, the frame furthercomprises a second end portion having a shape which is engageable with asecond side portion of the standard roofing tile.

In a further aspect of the present invention, the frame comprises afirst end portion having a shape which is similar to at least a firstside portion of a standard roofing tile. Preferably, the frame furthercomprises a second end portion having a shape which is similar to asecond side portion of the standard roofing tile.

The frame according to the present invention can be made of any suitablematerial. For example, the frame is preferably made of aluminum.

FIG. 2 depicts an example of a standard roofing tile 20, made, e.g, ofconcrete, The tile 20 depicted in FIG. 2 has a right side portion 21 anda left side portion 22. The right side portion 21 includes an overhangportion 23 and an overlay portion 24. The left side portion 22 includesan upright portion 25 and a trough portion 26. When installing suchroofing tile, a first tile is positioned on the roof with its topsurface 27 away from the roof, and then a second tile is positioned onthe roof, also with its top surface 27 away from the roof, such that theright side portion 21 of the second tile engages with the left sideportion 22 of the first tile, whereby the overlay portion 24 of thesecond tile is adjacent to or in contact with the upright portion 25 ofthe first tile, and the overhang portion 23 of the second tile isadjacent to or in contact with the trough portion 26 of the first tile.In some cases, each tile includes a bottom hanging portion (seereference no. 29 in FIG. 9) which hangs over a batten (see referencenos. 96 in FIG. 9) which has been attached to the roof deck, in order toassist in holding the tiles on the roof. In the tile 20 shown in FIG. 2,there are further provided holes 28 through which screws, nails, boltsor any other attachment element can be inserted and driven into orotherwise engaged with the roof deck to assist in holding the tiles onthe roof. Furthermore, one or more retaining clips (see reference nos.90 and 97 in FIG. 9) can be attached to the roof deck, the retainingclips including a portion which covers a portion of the top surface 27(preferably on the end remote from where the holes 28 are shown), toassist in holding the tiles on the roof (e.g., in high winds).

FIG. 3 depicts a front end of a first embodiment of a frame according tothe present invention, suitable for use in making photovoltaic tileswhich can be used, together with roofing tiles, e.g., tiles 20 as shownin FIG. 2, in constructing a roof. The frame includes a left end portion31 and a right end portion 32. FIG. 3 also shows top elements 33 of theframe and lower elements 34. The photovoltaic element (not shown in FIG.3) is positioned between the top elements 33 and the lower elements 34,the top elements 33 and the lower elements 34 supporting thephotovoltaic element and serving to assist in holding the photovoltaicelement in place. The left end portion 31 includes an upright portion 35and a trough portion 36. The right end portion 32 includes an overhangportion 37 and an overlay portion 38. Screws 39 connect the front framemember 40 to the left frame member 41 and the right frame member 42.

FIG. 4 is a view of the back side (i.e., the side opposite the frontface shown in FIG. 3) of the front frame member 40. FIG. 4 shows astiffening rib 43.

As used herein, the expression hook shape includes a shape which has abody portion, a hook portion and a connecting portion which connects thebody portion and the hook portion, the hook portion being spaced fromthe body portion in a first direction, the hook portion having at leastone dimension which is larger in a transverse direction perpendicular tothe first direction than a corresponding dimension on the connectingportion in the same transverse direction. As used herein, a statementthat a first structure has a hook shape which is engageable (or engaged)with a hook shape attached to a second structure means that therespective hook shapes are shaped such that they can be engaged witheach other so as to prevent the separate structures being from separatedfrom each other by either or both structures being moved in the “first”direction (as defined above).

As used herein, the expression upward hook shape includes a shape whichhas an upward hook portion which extends away from a main surface, theupward hook portion including an upwardly extending portion and aconnecting portion, the connecting portion connecting the upwardlyextending portion to the main surface. For example, the left sideportion 22 of the tile 20 depicted in FIG. 2 has an upward hook shape,as does the left end portion 31 of the first embodiment of a frameaccording to the present invention, depicted in FIG. 3.

As used herein, the expression downward hook shape includes a shapewhich has a downward hook portion which extends away from a mainsurface, the downward hook portion including a downwardly extendingportion and a connecting portion, the connecting portion connecting thedownwardly extending portion to the main surface. For example, the rightside portion 21 of the tile 20 depicted in FIG. 2 has a downward hookshape, as does the right end portion 32 of the first embodiment of aframe according to the present invention, depicted in FIG. 3.

When installing a photovoltaic tile as depicted in FIGS. 3 and 4adjacent to a roofing tile 20 as shown in FIG. 2, the photovoltaic tileis positioned on the roof such that the right end portion 32 of theframe of the photovoltaic tile engages with the left side portion 22 ofthe first tile, whereby the overlay portion 38 of the frame of thephotovoltaic tile is adjacent to or in contact with the upright portion25 of the roofing tile, and the overhang portion 37 of the photovoltaictile is adjacent to or in contact with the trough portion 26 of theroofing tile.

When installing a second photovoltaic tile as depicted in FIGS. 3 and 4adjacent to a first photovoltaic tile as depicted in FIGS. 3 and 4, thesecond photovoltaic tile is positioned on the roof such that the rightend portion 32 of the frame of the second photovoltaic tile engages withthe left side portion 31 of the frame of the first photovoltaic tile,whereby the overlay portion 38 of the frame of the second photovoltaictile is adjacent to or in contact with the upright portion 35 of theframe of the first photovoltaic tile, and the overhang portion 37 of theframe of the second photovoltaic tile is adjacent to or in contact withthe trough portion 36 of the frame of the first photovoltaic tile.

In FIGS. 5-7, a second embodiment of a frame according to the presentinvention is depicted.

FIG. 5 depicts profiles of a left end portion 51 and a right end portion52 of the second embodiment of a frame according to the presentinvention, suitable for use in making photovoltaic tiles which can beused, together with roofing tiles, in constructing a roof. The left endportion 51 provides an upward hook shape element which is engaged with aright end portion of a roofing tile 53, and the right end portion 52provides a downward hook shape element which is engaged with a left endportion of a roofing tile 54. The left end portion 51 and the right endportion 52 depicted in FIG. 5 each include a channel 55, which serves tocatch moisture, if any penetrates between the frame and the photovoltaicelement, and cause the moisture to drain out through the front of thephotovoltaic tile. The right end portion 52 shown in FIG. 5 isengageable with the left end portion of a second frame having a profileas shown in FIG. 5.

FIG. 6 is a profile of a front portion of the second embodiment of aframe according to the present invention.

FIG. 7 is a profile of a rear portion of the second embodiment of aframe according to the present invention. The rear portion includesholes 71 for receiving screws, nails, bolts or other connectors whichserve to attach the frame to the roof deck.

FIG. 8 depicts profiles of a left end portion 81 and a right end portion82 of a third second embodiment of a frame according to the presentinvention, suitable for use in making photovoltaic tiles which can beused, together with roofing tiles, in constructing a roof. The left endportion 81 provides an upward hook shape element which is engaged with aright end portion of a roofing tile 83, and the right end portion 82provides a downward hook shape element which is engaged with a left endportion of a roofing tile 84. The left end portion 81 and the right endportion 82 depicted in FIG. 8 each include a channel 85, which serves tocatch moisture, if any penetrates between the frame and the photovoltaicelement, and cause the moisture to drain out through the front of thephotovoltaic tile. The right end portion 82 shown in FIG. 8 isengageable with the left end portion of a second frame having a profileas shown in FIG. 8.

The respective end portions of the frames according to the presentinvention can be made of shapes which correspond to the shapes of theside portions of any suitable roofing tile, a wide variety of which areknown, e.g., various types of “shake” tile, concrete tile, “S” tiles(e.g, made of terra cotta), W tiles (e g, made of terra cotta), etc.

In a preferred aspect of the present invention, the width of the frame(i.e., the distance between respective end portions) is a multiple ofthe width of the roofing tile to which the end portions of the framecorrespond, so that each photovoltaic element can be mounted so as tooccupy an area which is the same or substantially the same as the areawhich would be occupied by a corresponding number (i.e., equal to themultiple) of roofing tiles, thereby providing the ability to providecontinuity in an overall pattern of a roof structure which includesroofing tiles and photovoltaic tiles.

Preferably, sealant material is applied between the frame and thephotovoltaic element to avoid seepage of water therebetween. Suitablesealant materials include, e.g., adhesives, preferably liquid adhesives,such as silicone sealant.

The present invention is also directed to a method of constructing aroof using a roofing system according to the present invention.

In accordance with the present invention, at least one photovoltaic tileis laid down on a roof together with a plurality of roofing tiles.Preferably, a layer of fire barrier roofing material is secured to theroof deck prior to laying down the tiles (i.e., the at least onephotovoltaic tile and the roofing tiles), so that the fire barrierroofing material is positioned between the roof deck and the tiles.Preferably, the layer of fire barrier roofing material is class C orbetter, e.g., class C, class B or class A. In such a case, the firebarrier roofing material preferably acts as the primary fire barrier andthe secondary weather barrier, while the tiles act as the primaryweather barrier. Any suitable type of barrier roofing material can beemployed, a variety of which are known in the building construction art,e.g., composite or asphalt shingles.

In a first embodiment of a method according to the present invention, aroof deck is attached to a support structure using nails, screws, boltsor any other suitable attachment members, as is well known in thebuilding construction art. The support structure can be any suitablebuilding material, e.g., wood. The roof deck can likewise be anysuitable building material, e.g., plywood or OSB.

In the first embodiment of a method, next, a layer of composite shinglesis applied to the roof deck, as is well known in the buildingconstruction art.

One or more battens are preferably secured to the roof before applyingthe tiles, preferably after applying fire barrier roofing material tothe roof so that the one or more battens (e.g., a 1 inch by 2 inch stripof wood) are positioned between the fire barrier roofing material andthe tiles. In such a case, the roofing tiles and/or the photovoltaictiles preferably have an anchor portion (e.g., on which a roofing tilewhich has a bottom hanging portion can be engaged) which abuts thebatten to serve to assist in holding the tile in place on the roof.

In the first embodiment of a method, a plurality of battens arepositioned on the composite shingles and attached to the roof deck.

Preferably, at least a first course of roofing tiles are applied alongthe bottom edge of the roof, and then a second course of roofing tilesare applied just above the first course, with a consistent amount ofoverlap. A typical roofing tile extends about 17 inches in the directiontoward the apex of the roof, and in such a case, the overlap ispreferably from about 3 to about 4 inches. Providing leeway in theamount of overlap increases the possibility that a uniform overlap canbe applied in the ascending courses of tiles, such that tiles completelycover the roof and each tile has approximately the same reveal length(i.e., the exposed area of each tile has approximately the samedimension in the direction ascending the slope of the roof). Withroofing tiles having a right side portion which fits into the left sideportion of a similar roofing tile, application of a course of tilesmoves from right to left across the roof.

Preferably, each course of tiles which includes photovoltaic tilesincludes at least two roofing tiles at both ends of the course.Preferably, with roofing tiles having a right side portion which fitsinto the left side portion of a similar roofing tile, and correspondingphotovoltaic tiles having a right end portion which fits into the leftside portion of a corresponding roofing tile or into the left endportion of a similar photovoltaic tile, moving from right to left acrossthe roof, at least two roofing tiles are applied, then the photovoltaictiles are applied, and then at least two more roofing tiles are applied,completing the course of tiles. However, it should be appreciated thatany desired pattern of roofing tiles and photovoltaic tiles can be made,and the roofing tiles and photovoltaic tiles can be applied in anydesired sequence.

Preferably, at least two courses of roofing tiles are applied adjacentto the apex of the roof. Thus, a preferred pattern includes a border atleast two roofing tiles deep along the outer periphery of the roof, andthe inner region defined by the border containing or consisting ofphotovoltaic tiles.

Preferably, the tiles in each course are offset from the tiles in theimmediately adjacent course or courses. For example, a first course oftiles is applied, and then the tiles in the second course of tiles areapplied such that the gaps between respective tiles in the second courseare offset from the gaps between respective tiles in the first course.Preferably, the distance of the offset is approximately half of thewidth of the roofing tiles, i.e., half the length of the edges which areparallel to the bottom edge of the roofline.

Preferably, one or more retaining clips for each photovoltaic tile areattached to the roof deck prior to positioning such photovoltaic tile onthe roof. For example, FIG. 9 shows a retaining clip 90 which is boltedinto the roof deck 91 such that the free end of the retaining clip 90projects over the roofing tile 92 from the previous course. After allthe retaining clips for the photovoltaic tile 93 have been attached (orthe retaining clip, where only one retaining clip is used for eachphotovoltaic tile), the photovoltaic tile 93 is moved into position onthe roof, with the free end of each retaining clip sliding between theframe of the photovoltaic tile 93 and an underhang portion 94 (anunderhang portion 94 is shown in FIG. 6 also) which is integral with orrigidly attached to the front portion of the frame of the photovoltaictile 93.

FIG. 9 also shows battens 96 attached to the roof deck 91.

Preferably, the frame includes a flange portion 95 (a flange portion 95is shown in FIG. 6 also) having at least one hole, for receiving a nail,screw, bolt or other attachment element which serves to attach the frameto the roof deck.

After the course of tiles which includes the photovoltaic tile 93 hasbeen completed, retaining clips 97, for the next course of tiles, areattached to the roof deck 91. The free end of the retaining clip 97projects over the photovoltaic tile 93 from the previous course. Afterall the retaining clips for the photovoltaic tile 98 have been attached,the photovoltaic tile 98 is moved into position on the roof, with thefree ends of the retaining clips sliding between the frame of thephotovoltaic tile 98 and the underhang portion 99 which is integral withor rigidly attached to the front portion of the frame of thephotovoltaic tile 98.

In the embodiment shown in FIG. 9, the underhang portion 99 extendsparallel to the free end of the retaining clip 97 for a distance whichmakes it possible to mount the tile 98 so as to provide the desired“reveal” (i.e., the exposed area) of the tile 93 below. Preferably, thereveal of each tile is in the range of from about 13 to about 14 inches.The retaining clip serves, e.g., to prevent uplift in windy conditions.

Preferably, as each photovoltaic tile is positioned, it is wired suchthat energy (from the conversion by the photovoltaic element of lightenergy into electrical energy) can be collected. In a preferred aspectof the invention, each photovoltaic tile has a pair of output wires, andas each photovoltaic tile is installed, its output wires are connectedto collection wires so that the photovoltaic tiles are connected inseries to collection wires. One end of each of the collection wirespreferably extends through the roof deck and into the interior of thebuilding, e.g,, to be connected to an inverter. Preferably, a structureis provided whereby the space in the roof deck through which thecollection wires pass is prevented from leaking, e.g., by use of anelbow structure with a bulkhead, such structures being known in the art.

Preferably, the photovoltaic tiles are grounded, e.g., by using a groundwire which is connected to the respective frames of each of thephotovoltaic elements. In such a case, the photovoltaic tiles arepreferably connected to the ground wire sequentially as the photovoltaictiles are installed.

Preferably, when a photovoltaic tile according to the present inventionis engaged with an adjacent photovoltaic tile or roofing tile, space isprovided which can accommodate expansion and shrinkage of the frame. Forexample, FIG. 10 shows a pair of photovoltaic tiles 101, 102 engagedwith each other, in which the right end portion of the photovoltaic tile101 is engaged with the left end portion of the photovoltaic tile 102.As shown in FIG. 10, space 103 is present between the frames which canaccommodate lateral expansion and contraction of the respective frames.FIG. 10 also shows a right end portion of photovoltaic tile 102 engagedwith a left side portion of a roofing tile 103, and, in a differentcourse, a roofing tile 104 having a right side portion engaged with aleft side portion of a roofing tile 105. From FIG. 10, it can be seenthat water which enters the space between the roofing tile 104 and theroofing tile 105 will tend to flow along that space (i.e., will notescape the trough portion of roofing tile 105 over the upright portionof the roofing tile 105) until it reaches the lower end of that courseof tiles, and then run out onto the roofing tile 103. Similarly, waterwhich enters the space between the roofing tile 103 and the photovoltaictile 102 will tend to flow along that space (i.e., will not escape thetrough portion over the upright portion of the left side portion of theroofing tile 103) until it reaches the lower end of that course oftiles, and then run out onto the tiles in the course below. Similarly,water which enters a space between a pair of photovoltaic tiles willtend to flow in that space (i.e., will not escape the trough portionover the upright portion of the left side portion of the photovoltaictile). In such a way, the combination of roofing tiles and photovoltaictiles provides an effective primary weather barrier.

In accordance with one modification of the present invention, some orall of the end portions of photovoltaic tiles which are engaged with endportions of other photovoltaic tiles have shapes which differ from theend portions of photovoltaic tiles which are engaged with side portionsof roofing tiles. Therefore, where a series of photovoltaic tiles areconnected to one another, it is only the end portions of thephotovoltaic tiles in that series which engage with roofing tiles thatneed to be shaped similar to the corresponding end portions of theroofing tiles. In this modification, three types of photovoltaic tilesare provided, one type for engaging a photovoltaic tile on its right endand a roofing tile on its left end, a second type for engaging aphotovoltaic tile on its right end and a photovoltaic tile on its leftend, and a third type for engaging a roofing tile on its right end and aphotovoltaic tile on its left end.

Preferably, each frame may include one or more drain holes or notchesfor the purpose of allowing any moisture which may have penetrated intothe photovoltaic tile to escape and/or to pass through the frame alongthe surface of the roof deck.

Preferably, the photovoltaic tiles are constructed and/or mounted so asto remain as cool as possible (i.e., to minimize temperature rise) usingany suitable technique, a wide variety of which are well known to thoseof skill in the art. For example, one such technique is to employconventional counter-battens, i.e., a first series of battens mounted onthe roof deck and running up the roof deck perpendicular to the roofapex, and a second series of battens mounted on the first series ofbattens and perpendicular to the first series of battens (i.e., parallelto the roof apex), and then to mount the tiles on the second series ofbattens.

Although the photovoltaic tiles, roofing systems and methods ofconstructing roofs in accordance with the present invention have beendescribed in connection with preferred embodiments, it will beappreciated by those skilled in the art that modifications notspecifically described may be made without departing from the spirit andscope of the invention defined in the following claims. For example, anytwo or more structural parts of the photovoltaic tiles and/or roofingsystems can be integrated; any structural part of the photovoltaic tilesand/or roofing systems can be provided in two or more parts (which areheld together, if necessary).

1. A photovoltaic tile, comprising: at least one photovoltaic elementhaving at least one photovoltaic collection surface; and a frame holdingsaid at least one photovoltaic element such that said at least onephotovoltaic element is substantially held in place relative to saidframe, said frame comprising a first end portion, a second end portion,a front frame surface and a back frame surface, said first end portionbeing of a shape which is engageable with a shape of said second endportion, said front frame surface and said back frame surface eachhaving a length which is a multiple of a length of a standard roofingtile, said multiple being an integer of at least two.
 2. A photovoltaictile as recited in claim 1, wherein said first end portion comprises anupward hook shape, and said second end portion comprises a downward hookshape.
 3. A photovoltaic tile, comprising: at least one photovoltaicelement having at least one photovoltaic collection surface; and a frameholding said at least one photovoltaic element such that said at leastone photovoltaic element is substantially held in place relative to saidframe, said frame comprising a first end portion, a second end portion,a front frame surface and a back frame surface, said first end portionhaving a shape which is engageable with at least a first side portion ofa standard roofing tile, said front frame surface and said back framesurface each having a length which is a multiple of a length of astandard roofing tile, said multiple being an integer of at least two.4. A photovoltaic tile as recited in claim 3, wherein said frame furthercomprises a second end portion having a shape which is engageable with ashape of said first end portion.
 5. A photovoltaic tile as recited inclaim 3, wherein said frame further comprises a second end portionhaving a shape which is engageable with a second side portion of saidstandard roofing tile.
 6. A photovoltaic tile, comprising: at least onephotovoltaic element having at least one photovoltaic collectionsurface; and a frame holding said at least one photovoltaic element suchthat said at least one photovoltaic element is substantially held inplace relative to said frame, said frame comprising a first end portion,a second end portion, a front frame surface and a back frame surface,said first end portion having a shape which is similar to at least ashape of a first side portion of a standard roofing tile, said frontframe surface and said back frame surface each having a length which isa multiple of a length of a standard roofing tile, said multiple beingan integer of at least two.
 7. A photovoltaic tile as recited in claim6, wherein said frame further comprises a second end portion having ashape which is similar to a shape of a second side portion of saidstandard roofing tile.
 8. A roofing system, comprising: at least onephotovoltaic tile as recited in claim 5, said photovoltaic tile furthercomprising at least one underhang portion attached to or integral withsaid frame; and at least one retaining clip, said retaining clipcomprising an underhang engaging portion having a thickness which issmaller than a thickness of a space between said underhang portion andsaid frame.
 9. A roofing system as recited in claim 8, wherein saidretaining clip has a first substantially flat portion for engagementwith a roof deck, an underhang engaging portion for fitting between saidunderhang portion and said frame, and a third portion connecting saidfirst portion to said underhang engaging portion.
 10. A roofing system,comprising: a plurality of roofing tiles, each said roofing tile havinga first side portion and a second side portion; and at least onephotovoltaic tile as recited in claim
 5. 11. A roofing system,comprising: at least one photovoltaic tile as recited in claim 7, saidphotovoltaic tile further comprising at least one underhang portionattached to or integral with said frame; and at least one retainingclip, said retaining clip comprising an underhang engaging portionhaving a thickness which is smaller than a thickness of a space betweensaid underhang portion and said frame.
 12. A roofing system as recitedin claim 11, wherein said retaining clip has a first substantially flatportion for engagement with a roof deck, said underhang engaging portionfor fitting between said underhang portion and said frame, and a thirdportion connecting said first portion to said underhang engagingportion.
 13. A roofing system, comprising: a plurality of roofing tiles,each said roofing tile having a first side portion and a second sideportion; and at least one photovoltaic tile as recited in claim
 7. 14. Amethod of constructing a roof, comprising: positioning at least oneroofing tile on a roof surface, said at least one roofing tile having afirst side portion; and positioning at least a first photovoltaic tileon said roof surface, said first photovoltaic tile comprising a firstphotovoltaic element and a first frame, said first frame holding saidfirst photovoltaic element such that said first photovoltaic element issubstantially held in place relative to said first frame, said firstframe comprising a first end portion, such that said first end portionof said first frame is engaged with said first side portion of said atleast one roofing tile.
 15. A method as recited in claim 14, furthercomprising attaching at least one retaining clip to said roof deck, saidframe having an underhang portion attached thereto, and whilepositioning said at least one photovoltaic tile on said roof surface, afree end of said retaining clip slides between said frame and saidunderhang portion.
 16. A method as recited in claim 15, wherein anunderhang engaging portion of said retaining clip overlaps only aportion of said underhang portion, whereby a first photovoltaic tile inone course can be mounted on said roof surface above a secondphotovoltaic tile in a different course such that a desired reveallength of said second photovoltaic tile is not overlapped by said firstphotovoltaic tile.
 17. A method as recited in claim 14, furthercomprising: positioning at least a second photovoltaic tile on said roofsurface, said second photovoltaic tile comprising at least a secondphotovoltaic element and a second frame, said second frame holding saidsecond photovoltaic element such that said second photovoltaic elementis substantially held in place relative to said second frame, saidsecond frame comprising a second frame first end portion and a secondframe second end portion, such that said second frame first end portionis engaged with a second end portion of said first frame.
 18. A roofingsystem, comprising: a plurality of roofing tiles, each said roofing tilehaving a first side portion and a second side portion; and at least onephotovoltaic tile, said photovoltaic tile comprising: at least onephotovoltaic element having a photovoltaic collection surface, and aframe holding said at least one photovoltaic element such that said atleast one photovoltaic element is substantially held in place relativeto said frame, said frame comprising a first end portion and a secondend portion, said first end portion being engaged with said first sideportion of one of said roofing tiles.
 19. A roofing system, comprising:at least a first photovoltaic tile and a second photovoltaic tile, saidfirst photovoltaic tile comprising: at least a first photovoltaicelement having a first photovoltaic collection surface, and a firstframe holding said first photovoltaic element such that said firstphotovoltaic element is substantially held in place relative to saidfirst frame, said first frame comprising a first frame first end portionand a first frame second end portion, said second photovoltaic tilecomprising: at least a second photovoltaic element having a secondphotovoltaic collection surface, and a second frame holding said secondphotovoltaic element such that said second photovoltaic element issubstantially held in place relative to said second frame, said secondframe comprising a second frame first end portion and a second framesecond end portion, said first frame first end portion being engagedwith said second frame second end portion, a space being located betweensaid first frame first end portion and said second frame second endportion such that said first frame can move relative to said secondframe such that said first photovoltaic element moves closer to saidsecond photovoltaic element.
 20. A photovoltaic tile, comprising: atleast one photovoltaic element having at least one photovoltaiccollection surface; a frame holding said at least one photovoltaicelement such that said at least one photovoltaic element issubstantially held in place relative to said frame; and an underhangportion, said frame comprising a first end portion and a second endportion, said first end portion being of a shape which is engageablewith a shape of said second end portion, said underhang portionconsisting of a first underhang element and a second underhang element,said first underhang element being substantially planar and beingsubstantially parallel to a surface of said frame, said second underhangelement extending from said frame to said first underhang element.
 21. Aroofing system, comprising: at least one photovoltaic tile comprising:at least one photovoltaic element having at least one photovoltaiccollection surface; and a frame holding said at least one photovoltaicelement such that said at least one photovoltaic element issubstantially held in place relative to said frame, said framecomprising a first end portion, a second end portion and an underhangportion, said first end portion having a shape which is engageable withsaid second end portion; and at least one retaining clip, said retainingclip consisting of a roof-engaging portion, a transition portion and anunderhang engaging portion, said underhang engaging portion beingsubstantially planar, said transition portion extending from saidroof-engaging portion to said underhang engaging portion, each of saidroof-engaging portion, said transition portion and said underhangengaging portion being substantially flat, said underhang engagingportion engaging said underhang portion.
 22. A roofing system,comprising: a plurality of roofing tiles, each said roofing tile havinga first side portion and a second side portion; at least onephotovoltaic tile comprising: at least one photovoltaic element havingat least one photovoltaic collection surface; and a frame holding saidat least one photovoltaic element such that said at least onephotovoltaic element is substantially held in place relative to saidframe, said frame comprising a first end portion, a second end portionand an underhang portion, said first end portion having a shape which isengageable with said second end portion; and at least one retainingclip, said retaining clip comprising an underhang engaging portion,wherein: said first end portion of said photovoltaic tile is of a shapewhich is engageable with said first side portion of said roofing tiles,said second end portion of said photovoltaic tile is of a shape which isengageable with a second side portion of said roofing tiles, saidphotovoltaic tile is positioned above said retaining clip such that saidunderhang engaging portion of said retaining clip is positioned betweena portion of said underhang portion and a portion of said frame, andsaid underhang engaging portion of said retaining clip is positionedabove at least a portion of a first of said roofing tiles such that saidportion of said underhang portion and said underhang engaging portionare positioned between a portion of said first roofing tile and aportion of said frame.
 23. A roofing system as recited in claim 22,wherein said underhang portion comprises an underhang element which issubstantially parallel to a plane defined by a bottom of said frame. 24.A roofing system as recited in claim 22, wherein said underhang portionconsists of a first underhang element and a second underhang element,said first underhang element being substantially planar and beingsubstantially parallel to a surface of said frame, said second underhangelement extending from said frame to said first underhang element.
 25. Aroofing system as recited in claim 22, wherein said retaining clipconsists of a roof-engaging portion, a transition portion and saidunderhang engaging portion, said underhang engaging portion beingsubstantially planar, said transition portion extending from saidroof-engaging portion to said underhang engaging portion, each of saidroof-engaging portion, said transition portion and said underhangengaging portion being substantially flat.